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Taxes

Estimated tax penalty calculator

The IRS underpayment penalty is not a fine, it is interest: each quarterly installment you miss accrues at the federal underpayment rate (7% for Q3 2026, checked 2026-08-23 against irs.gov) from its due date until April 15. Enter your required annual payment and what you actually sent each quarter to see the damage per period, and whether catching up now is worth it. It usually is: interest stops on every dollar the day you pay it.

Your payments for tax year 2026
$

The smaller of 90% of this year's tax or your safe-harbor amount; our safe harbor calculator computes it.

$

Estimated tax actually sent by each due date, withholding included.

$

Estimated tax actually sent by each due date, withholding included.

$

Estimated tax actually sent by each due date, withholding included.

$

Estimated tax actually sent by each due date, withholding included.

Underpayment interest

Estimated penalty$339.45

From Apr 15, 2026
$50.14
From Jun 15, 2026
$86.03
From Sep 15, 2026
$116.99
From Jan 15, 2027
$86.3
Total still underpaid
$5,000

Estimate

workingfigures.com/calculators/estimated-tax-penalty-calculator

Formula

Each installment is 25% of the required annual payment. For every period between due dates, interest = shortfall × rate ÷ 365 × days, where the rate is the IRS underpayment rate in force (federal short-term rate + 3 points, set quarterly: 7% in Q1 2026, 6% in Q2, 7% in Q3). Payments count against the oldest shortfall first.

Assumptions

This is the Form 2210 chart method: payments are assumed to land on their due dates, installments are equal quarters (no annualized-income method for lumpy years), and interest runs to the April 15, 2027 deadline. Quarters the IRS has not yet published (Q4 2026 onward) carry the last known 7% forward. Rates checked 2026-08-23 against irs.gov/payments/quarterly-interest-rates; we review them every quarter.

FAQ

How much does skipping one $5,000 quarter actually cost?
Less than the fear suggests, more than zero: skip the April 2026 installment of a $20,000 year and never catch up, and the tool shows about $339 of interest by April 2027. The same shortfall caught up by June 15 costs about $50. The penalty scales with time, which is why a late payment now always beats a bigger payment in April.
Is this the same as the failure-to-pay penalty?
No. This tool computes the section 6654 estimated-tax penalty, which applies while the year is still in progress even if you file on time. The separate failure-to-file and failure-to-pay penalties only start after the filing deadline, and they stack on top of this one if you also file or pay late.
Can the penalty be waived?
Sometimes. There is no penalty at all if you owe under $1,000 after withholding, or if you met a safe harbor: paying 100% of last year's tax (110% above $150,000 AGI) or 90% of this year's. The IRS can also waive it after a disaster, a casualty, or retirement or disability during the year; that goes on Form 2210 with an explanation, not through this calculator.